Finally.... TN70DA

[RickB]

Like Andy says, the AC should freeze you out. Instead of checking the system pressure, why not just check the air temp at the cab vents? A good TN system should vent air from the evaporator nearly 30 degrees below ambient as measured in front of the condenser. Anything less than 20 degrees drop indicates a problem. The Schrader valves are a fairly common source of leakage; I have changed more than a couple. Also, if it were shipped low on charge without any leak, that wouldn't be the first. I would call the dealer before you hook service gauges up. I know I would prefer to troubleshoot a system that hadn't been touched to one that had, regardless of your abilities and intentions.

 

[Rowski]

Looked into the a/c tonight. Hooked up the a/c gauges and found the pressures to be a bit abnormal. Recover the refrigerant and found it to be over charged by about 1 lb. I figured great! That's my problem. Not so. It cooled even better at idle and off idle now. But still lacked cooling at higher engine rpms. The gauge pressure are now normal durning cooling and even at the higher rpms when there is no cooling. Anything under 1400 to 1500 rpms and it cools very nicely. Anything over 1400 to 1500 rpms and the cooling is gone and the air is like luke warm. Now with the a/c off for a while (evaporator core warmed) at idle the fan will blow "cool" out side air with a/c off. Bring the rpms back up with the a/c off and the fan on the air becomes luke warm again. Now the temp control switch does respond when moved to the hot position, blows hot air, even at higher rpms. So my thinking is something with the heater flow control valve. I'm not sure if there is one.

As far as the 4wd light. It does not come on. But during braking I can feel the front wheels engage during braking and see the marks on the dirt road. I can sweat that during my a/c diagnosis tonight I saw the 4wd light on during a key on engine off event. I did check the fuses look ok. I do get the brake light relay to click when applying the brakes. I also get the two relays (same bottom row) next to the brake light relay to click, I believe those are for differential lock disengagement during braking. I did verify that on the trailer connector there is no power on the terminal for stop lights. I didn't check the relays for powers and grounds yet. I was getting Pi$$ed at this point.


Any Ideas??

I know... I should call my dealer but they will want the tractor back and keep it for a while. I don't mind spending the time to fix it if I have some general direction to go. I did order a factory service manual but its not here yet.

Thanx.

 

[Rowski]

RickB

The dealer was more than happy to have me trouble shoot the a/c system. Told me to send him a bill and he would give me a check or trade filters or what ever. He also thought as I did it would be low on charge. But it was actually over charged.

 

[RickB]

The heater control is a cable operated coolant valve at the heater core. This cable is the only thing connected to the large left hand hot/cold knob. Sounds as if the valve may not be closing completely and is bypassing hot coolant, especially at higher RPM's. Easiest way to check is pinch off a heater hose somewhere near the bottom of the A pillar. The headliner will need to come down to get anywhere near the valve. Consider taking vent temps as I suggested yesterday to help evaluate AC performance on these cooler days. Glad to hear your dealer is on board with you. Send me a PM or post back here if I can help.

 

[Rowski]

Some more pictures

 

[Rowski]

Another

 

[Rowski]

more

 

[Rowski]

Another with the 2120 next to it.

 

[Rowski]

Another with the 2120

 

[Rowski]

Mre with 2120.